1. Field of the Invention
The present invention relates generally to dental implants and, more particularly, methods and devices for taking an impression of a final abutment, which is attached to a dental implant.
2. Description of the Related Art
Restoration of an edentulous area of the mouth serves multiple functions, including improved aesthetics, improved mastication, maintenance of crestal bone, and providing for an occlusal stop for a reproducible bite. Restoration can be accomplished using a standard bridge, a removable appliance (a partial or full denture), or a dental implant.
Dental implantation is a procedure for replacing a missing tooth using a dental implant. The placement of the implant is usually accomplished in four stages. In a first stage, a dentist reviews radiographs and dental models to determine the proper placement and axial alignment of the implant. In a second stage, a dental surgeon accesses the bone through the mucosal tissue. With the use of a prefabricated stint, the surgeon drills or bores out the maxillary or mandibular bone. The implant is then either pressed or screwed into the bone. A healing cap is typically then placed over the implant and the surrounding mucosal tissues are sutured over the healing cap. This provides for a biologically closed system to allow osteointegration of bone with the implant. Complete osteointegration typically takes anywhere from four to ten months.
Stage three, involves a second surgical procedure during which the dental surgeon makes an incision in the mucosal tissue to expose the osteointegrated implant. The healing cap is removed and a temporary abutment, having a height at least equal to the thickness of the gingival tissue or a final prosthetic abutment, is coupled to the implant. Once the abutment is secured an immediate mold or impression may be taken. In a modified procedure, the impression may be taken within one to two weeks after the stage three. The impression is used to record the axial position and orientation of the implant, which is then reproduced in a stone or plaster analogue of the patient""s mouth. The main objective of the impression is to properly transfer the size and shape of adjacent teeth in relation to the permanently placed implant and the precise configuration and orientation of the abutment to the dental technician. The plaster analogue provides the laboratory technician with a precise model of the patient""s mouth, including the orientation of the implant fixture relative to the surrounding teeth. Based on this model, the technician constructs a final restoration. Stage four, in the restorative process, involves replacing the temporary healing abutment with the final restoration.
As noted above, during stage three, a mold or impression is taken of the patient""s mouth to accurately record the position and orientation of the implant site and to provide the information needed to fabricate the restorative replacement and/or intermediate prosthetic components. There are several conventional methods for taking the this impression.
One method involves a conventional transfer coping. Transfer copings have an impression portion adapted to form a unique or indexed impression in the impression material and a base portion having mating indexing means adapted to mate with the exposed indexing means of the implant or prosthetic abutment. In use, the transfer coping is temporarily secured to the exposed proximal end of the implant fixture such that the mating indexing means of the impression coping and implant are interlockingly mated to one another. Typically, a threaded screw or bolt is used to temporarily secure the transfer coping to the implant fixture.
Once the impression coping is secured to the implant fixture, an impression of the transfer coping relative to the surrounding teeth is taken. Typically, this involves a xe2x80x9cUxe2x80x9d shaped tray filled with an impression material that is placed in the patient""s mouth over the implant site. The patient bites down on the tray, squeezing the impression material into the implant site and around the transfer coping. Within a few minutes, the impression material cures or hardens to a flexible, resilient consistency. The impression tray is then removed from the patient""s mouth to reveal an impression of the implant site and the transfer coping. The restorative dentist then removes the transfer coping from the patient""s mouth and transfers the transfer coping back into the impression material, being careful to preserve the proper orientation of the indexing means.
Another method typically involves a conventional pick-up coping. Pick-up copings are similar to the transfer copings described above; except that a pick-up coping typically includes an embedment portion adapted to be non-removably embedded within the impression material. Typically, the embedded portion comprises a protuberant xe2x80x9clipxe2x80x9d or similar embedment projection at a coronal portion of the coping. This allows for xe2x80x9cgrabbingxe2x80x9d or traction of the impression material as the tray is being removed from the patient""s mouth. The pick-up copings are xe2x80x9cpicked upxe2x80x9d and remain in the impression material when the tray is removed from the patient""s mouth.
Yet another method for taking an impression involves an impression or transfer cap. Impression or transfer caps are placed over or on the built-up part of the abutment or the implant and remain in the impression material when the tray is removed. There are several different types of transfer caps. One type of transfer cap has a tapered inner surface, which is adapted in form and size to the built-up part or abutment of the implant. This cap has an inner surface, which has indentations or slots, which correspond to indentation or slots present on the abutment. The cap is attached to the abutment with resilient flaps or tongues. An example of such a cap is illustrated in U.S. Pat. No. 5,688,123. A disadvantage to this type of cap is apparent when the abutment is modified in vitro to create axial draw parallel to adjacent teeth and/or implants. If the abutment is modified, the transfer cap may not represent an accurate impression of the abutment because the indentations or slots may have been mechanically removed during the modification. Therefore, this method does not necessarily accurately reproduce the size and shape of a modified abutment.
Additionally, there are transfer caps which are capable of recording modifications in abutments. These caps typically have a large aperture or hole (diameter greater than ⅓ of the area of the axial wall of the cap) in the distal end (occlusally) for placement or injection of impression materials. Moreover, such impression caps have large apertures or holes on the axial walls to allow excess gas and impression material to escape. They may also utilize a sleeve that inserts inside the impression caps to facilitate recording the slots and recesses of an unmodified abutment. A disadvantage of these types of impression caps is that an excessive amount of impression material gets displaced through the large holes or apertures leaving air bubbles and voids, which reduce the accuracy of the impression.
Accordingly, one aspect of the present invention is an impression cap for taking dental impressions in a patient""s mouth. The impression cap comprises a distal end that includes a top surface, a proximal end that defines an opening, and an inner surface that defines an internal cavity. The proximal end of the impression cap is configured to engage a corresponding shoulder of a prosthetic abutment. The impression cap further comprises an injection port configured to receive a tip of an injection syringe for injecting impression material into the inner cavity and a plurality vent holes configured to allow air and excess impression material to escape from the inner cavity.
Another aspect of the present invention is a dental kit for replacing a missing tooth with a dental prosthesis. The dental kit includes an abutment configured to mate with a dental implant, a coupling screw configured to extend through an inner bore of the abutment so as to couple the abutment to the dental implant, a healing cap with an internal cavity configured to fit over the abutment, a healing cap screw configured to couple the healing cap to the abutment, an impression cap configured fit over the abutment cap, the impression cap including an injection port and a plurality of bleed holes, and a syringe tip configured to mate with the injection port of the impression cap.
Yet another aspect of the present invention is a method for taking a dental impression in a patient""s mouth comprising providing an impression cap with an injection port and a plurality of vent holes, positioning an impression cap onto a prosthetic abutment; and injecting a first impression material into the impression cap through the injection port until the first impression material is extruded through at least one of the vent holes.
Still yet another aspect of the present invention is a method for taking a dental impression in a patient""s mouth. The method comprises the step of providing a first set and a second set of components, the first set including an abutment configured to mate with a dental implant in a patient""s mouth, a coupling screw configured to extend through an inner bore of the abutment so as to couple the abutment to the dental implant, a healing cap with an internal cavity configured to fit over the abutment, and a healing cap screw configured to couple the healing cap to the abutment, the second set including an impression cap configured fit over the abutment cap and having an injection port and a plurality of bleed holes and a syringe tip configured to mate with the injection port of the impression cap. The method also comprises coupling the abutment to the dental implant with the coupling screw, coupling the healing cap to the abutment with the healing cap screw; and providing the patient with the second set of components.
Further aspects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments.